I'm not familiar with using third-party dictionaries on the Kindle 3, at least not as the lookup dictionary for when reading a book. I do know that many of the eBook reading apps for iOS (iPad/iPhone) and Android have lookup dictionaries with a button you can press to hear the word pronounced. But I know of no eInk reader with this native ability.

BTW, The Kindle 3 dictionary does have pronunciation symbols if you expand the small lookup window to fullscreen, but it will not sound out the word AFAIK.

Unfortunately, text-to-speech does not always pronounce words correctly, so I wouldn't want to rely on it to pronounce dictionary words correctly.

The K1's dictionary showed the International Phonetic Alphabet version of how to pronounce words, when you clicked on the word detail. I understand that is no longer the case, which is too bad.

K3 has two dictionaries, the New Oxford American Dictionary does have IPA spelling if you actually go to the dictionary listing. I have several 3rd party dictionaries, TTS is not enabled in any of them. It's not a DRM restriction, just a 'feature' of TTS apparently.

It's not clear why you'd need the dictionary to have TTS pronounce the word, if it is in the text then just use the TTS there. If there's something in the dictionary you want TTS to read, you can create a highlight, then find this in My Clippings and use TTS there. Not very convenient but ...

That's nice to know about the NOA dictionary having the pronunciation guide. I had not heard that before. Maybe a lot of Kindle users use the other dictionary? I've long been used to dictionary IPA versions of pronunciation, so that works great for me, if I ever upgrade to a K3 or 4 (when it comes out).